Early E46's did NOT come equipped with DRIVE BY WIRE.
The cable its not a Back up for a drive by WIRE system. It controls the throttle like all the older models.

Maybe I used the wrong wording, but it's not a regular throttle cable based system like on the M20. The cable doesn't actually pull on the throttle butterfly like a traditional throttle. The throttle is electronically controlled based on the input from the cable.